Numbers of species. Due to their bright colors and visits
to flowers, butterflies are the most familiar of insects to humans. There are about 17,500
species of butterflies in the world, and around 750 species in the United States.

Distinctive characteristics. Butterflies (and moths) are the
only group of insects that have scales covering their wings, although some butterflies
have reduced scales. They differ from other insects also by their ability to coil up their
proboscis.

Immatures. Caterpillars are the names given to the larvae of
both butterflies and moths. They are usually very distinctive, and in some cases may be
identified more easily than the adults. When they are developing, their skin may be shed
four or more times, with each molt often changing the coloration and appearance of the
caterpillar. They eat voraciously to transform plant material into tissues that they will
need for metamorphosis.

Plant associations. Butterflies are commonly associated with
plants, and the relationship is sometimes complex. Immatures, with few exceptions, eat
plants, and therefore may be considered harmful to the plants. However, butterflies are
very important to many plants that are dependent upon flower-visiting insects for
cross-pollination. Most butterfly caterpillars eat one, or sometimes several, related
species of plants. Usually the choice is made by the adult female when depositing eggs.
Adults usually feed on nectar from flowers of plants, although many butterflies feed
instead on rotting fruit, dung, etc., especially in the tropics.

Seed pods of Swamp Milkweed,
(Asclepias incarnata): an integral part of the Monarch Butterfly's life. Photographed in
the Butterfly Garden Habitat of the Smithsonian's National Museum of Natural History.
Smithsonian Photo by Michelle Baker. (c) 1995 Smithsoniaan Institution.

Migration. Butterfly migration is best exemplified by the
Monarch, which is widely known to migrate in the fall to overwintering sites in California
and Mexico. But in the United States, several other butterfly species engage in lesser
migration distances. Some of these are the Buckeye, the Painted Lady, the Purple Wing, the
Great Southern White, the Cloudless Sulphur, and the Little Sulphur.

Wing colors in butterflies appear in two types, pigment and
structural, frequently combined in one individual. Pigment colors are familiar in paints,
dyes, and inks, and are defined as specific substances with definite chemical composition.
Structural colors are instead produced in a physical manner, similar to a rainbow. Morpho
butterflies are the usual example of butterflies with structural color.

Vision. The vision of butterflies appears to be excellent,
especially within short distances. They are able to fly with precision in areas of many
obstacles.

Mating Behavior. Females are usually able to engage in mating on
the day of emergence, but males do not normally mate for several days. Courtship rituals
vary widely among species.